The invention is based on a fuel injection device as defined hereinafter. A fuel injection device of this kind is known, for instance from German Offenlegungsschrift No. 30 02 851, although this device is intended exclusively for an application where a primary fuel that is difficult to ignite pumped by a high-pressure injection pump, on the one hand, and on the other, an igniting fuel pumped by a separate pump are to be delivered via a hydraulically actuated auxiliary pump to separate injection nozzles, for the main fuel and the igniting fuel, in a Diesel engine. The low-pressure pump which furnishs the igniting fuel communicates with a pilot storage chamber in the auxiliary pump that is defined by an expulsion piston, and the supply pressure of the main fuel acts upon the remote side of the expulsion piston. Aside from the engineering expense necessary in order to provide each cylinder of the Diesel engine with separate injection valves for the pilot injection and the main injection, each with an auxiliary pump, and the many connecting lines needed for this, it is also problematical in the known apparatus to effect accurate control of the sequence of time between the pilot injection and the main injection, because the dead spaces existing in the connecting lines cause unavoidable deviations, particularly in accordance with rpm, from the specified control times for the pilot injection and the main injection.
An apparatus is also known (German Pat. No. 1 252 001) in which a separate, small piston for the pilot injection is disposed such that it is offset in an axially parallel manner from a loading piston for the main injection inside a fuel injection valve, although no separate low-pressure supply means is provided, and the pilot injection quantity is derived from the supply of fuel for the main injection. As a result, the standing pressure in the pressure line, and thus the accuracy of quantity control, are unfavorably affected.
Finally, it is also known (German Offenlegungsschrift No. 28 34 633), for controlling the pilot injection in internal combustion engines, to provide a one-piece control slide which is displaceable counter to the force of a spring, and which with a pronounced intermediate relief into a reservoir, via control edges, establishes the particular desired connections for the pilot injection and the main injection. Here again, the pilot injection quantity is diverted from the supply quantity of the injection pump that also furnishes the main injection quantity, so that once again the accuracy of the quantity control of the main injection quantity is affected negatively.